The invention set forth herein relates to a disposable and lightweight air filter having a relatively large flow through capacity and filter area which is adapted to fit within a relatively small space such as the engine compartment of a truck. The air filter is also constructed to withstand engine vibration and other stress conditions connected with the operation of a large high horsepower engine.
The necessity of filtering the intake air for internal combustion engines to prevent damage and premature wear is well known. For large trucks, there are a number of factors which dictate the necessity of providing an intake air filter having high dust removal efficiency such as: the high cost of the truck engine; the adverse environmental conditions commonly encountered; the high number of operating hours; the expected dependability of engine operation, etc. Moreover, the high volumetric rate of air injection of an internal combustion engine for large trucks requires the air filter to have high air flow capacity. As a result of these requirements, the conventional air filters for large trucks are usually of such a large size to preclude the mounting of the filter directly on the engine or, in many situations, even within the engine compartment. Thus, ducting must be provided for conducting the air from the filter to the intake which produces an air pressure drop and results in a reduction in engine efficiency. Moreover, this ducting is prone to develop leaks and admit unfiltered air to the engine.
Filter assemblies have been developed which meet the required filter area necessary for high dust removal efficiency and yet are sufficiently compact to be mounted directly on the engine. Examples of such filters include those which are described and claimed in U.S. Pat. Nos. 3,831,355 and 3,802,169 and in a filter marketed by Donaldson Co., Inc. of Minneapolis, Minn. under its trademark "Konepac". While these factors can be mounted directly on the engines, they, like the conventional air filters for large trucks, are quite heavy and rather expensive to manufacture. The weight of an air filter on a truck is particularly significant in view of the large number of miles over which such vehicles are driven and the added strain on the truck and its engine caused by any additional weight.
The problems of weight and cost found in the existing compact filters adapted for use on trucks result from their construction wherein a relatively heavy cartridge which holds and supports the filtering media is in turn mounted in an even heavier outer housing. It would be highly desirable to provide an air filter which had sufficient flow through capacity in the filtering area for use on large trucks and was sufficiently compact such that it could be mounted directly on the engine, yet was very light in weight and so economical to manufacture that the filter assembly could be disposable. To this end it would also be desirable to provide a reusable air inlet coupling to obviate the need for including such a device on the disposable filter thereby further reducing the cost of replacement. The present invention provides such a filter assembly.
Another problem associated with such filter assemblies is the installation of the moisture separator which is necessary to prolong the useful life of the filter. The configuration of such devices often require considerable piping to allow gravity to draw the moisture to the pipe walls for separation from the air flow. As quite often not enough space is available for the length necessary to utilize gravity, elbows are required in the pipe line to take advantage of the momentum of the water in the moving air for separation. The use of such elbows not only creates additional installation problems but still necessitates the filter element being spaced several diameters from the elbow to avoid an increase in the pressure drop which is, of course, undesirable. In addition to installation problems, many of the moisture separators through the nature of their construction create an increase in pressure drop. The present invention not only additionally solves the installation problems associated with such filter assemblies but also provides a moisture separator which has no appreciable effect on the pressure drop of the filtration system.